Bottlenecking GPU(s) at processor?

I'm about to buy a new notebook to use for school, though I do intent to do a heavy amount of gaming on it as well. I was looking at getting an m9700, but in order to afford dual GPUs I have to sacrifice the ml44 to one of the lesser options.

My concerns are threefold:

First, with the smaller cache size (512mb) of the ml42, is it even worth upgrading from ml34? (1.8ghz -> 2.4ghz; I admittedly know nothing about cache's impact on performance, or even how newer processors work in general). Cost of upgrade is $100.

Second, I've heard that even the ml44 will be the bottleneck in a SINGLE 7900GS configuration, let alone SLI. If that's the case, do I bother with the 2nd GPU? Or even worry about ml44 vs ml34?

And last, would I see a very drastic decrease in performance if I went to a t7200 c2d running a 7600 go (m5550)? saves a lot of money, but if SLI with the slower processor will last me longer...

Any input would be much appreciated! And sorry if this is the wrong forum! I found 3 or 4 places that it seemed to fit, but since this is primarily a processor question I put it here. I will gladly move if needed.

 

that M9700 laptop is such a weird setup.
They offer SLi 7900GS Go, but they don't even offer a dual core processor.

I feel uneasy about spending a fortune on a SLI 7900GS go laptop that don't even have a dual core processor.

that M5550 is also not a good buy, a Vostro 1500 with 8600M GT with whatever processor you want will perform better and cost less.

 

The m9700 is not worth it, at all.

If you really want an alienware, get the m9750, though a better choice would probably be the Clevo M570Ru, or the Clevo D900c (if you want the best).